A crackdown on Colorado medical-marijuana patients could trim the number of marijuana plants being legally grown in the state by tens of thousands, according to new figures from the state Health Department.

The crackdown focuses on patients authorized to grow more than the standard number of marijuana plants, as many as 99 plants for some. While those patients make up only about 2 percent of the state’s 111,000 registered patients, the patients are authorized to grow more than 85,000 marijuana plants — nearly 12 percent of the total plants that registered medical-marijuana plants are allowed to grow.

The state’s new scrutiny of patients with large plant counts comes after an audit last year warned that such patients may be “distributing the excess marijuana to individuals without (medical-marijuana) cards.”

But medical-marijuana advocates say the crackdown could also have far-reaching impacts on patients who use the higher-than-normal plant counts to create concentrated treatments, which they say help the most serious conditions. And the crackdown could also affect the supply for medical-marijuana dispensaries, which are limited in how much marijuana they can grow by the plant counts of the patients who have designated the stores to grow for them.

“Patients have done nothing wrong here,” Teri Robnett, a medical-marijuana advocate and patient who is authorized to grow 24 plants, said last week during a meeting where officials announced the crackdown. “And yet patients will be the ones who suffer.”

The controversy reaches deep into the folds of Colorado’s wrinkled marijuana laws.

Patients on the state’s medical-marijuana registry are typically authorized to grow six marijuana plants — with no more than three of those ready for harvest at any given time. But doctors can recommend that patients grow more plants if it is “medically necessary.”

In response to the audit, Colorado Health Department officials this week began sending out letters to doctors and medical-marijuana patients, warning them that the state will now require better documentation before it authorizes patients to grow more than the standard number of plants.

Among registered patients who have designated a caregiver, 2,822 patients have plant counts over six, according to Health Department numbers. The average plant count for those patients is more than 30, and there are 93 patients authorized to grow 99 plants. Last year’s audit mentions one patient whose doctor had recommended 501 plants.

At last week’s meeting, Dr. Larry Wolk, the executive director of the Colorado Department of Public Health and Environment, said most patients don’t need more than six plants even if they are making concentrated treatments.

“The technology has really advanced,” he said.

But James Clark Jr., a medical-marijuana patient and provider to two dozen other patients on Colorado’s eastern plains, sharply disputed that. Clark — who cares for 25 patients, including one authorized for 99 plants — said how many plants are needed to make concentrated marijuana oil depends on the growing technique, the strain being grown, the grower’s skill, the extraction method and any number of other factors.

All told, he said, it can take more than six ounces of marijuana — perhaps three plants’ worth — to produce six grams of marijuana oil. And that amount of oil might only last some patients a week.

“This is about caring for some very, very, very sick people,” Clark said.

Mark Salley, a Health Department spokesman, said the new documentation requirements will apply when medical-marijuana patients register with the state for the first time as well as when existing medical-marijuana patients renew their registrations each year.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold

Ninety-nine pot plants

Depending on several factors, 99 marijuana plants could produce as many as 12,000 joints.